Waste reduction systems have been in use for many years. A typical system includes a pulper unit, such as the SP-75S pulper manufactured by the Somat.RTM. Corporation of Coatesville, Pa., and a liquid extraction unit, such as the HE-6S Hydra Extractor.RTM. unit produced by the same manufacturer.
In a typical pulper system, kitchen waste is placed into a large cylindrical tank partially filled with water. A cutting mechanism is installed at the bottom of the tank. The cutting mechanism includes a rotating impeller plate with rotating blades that periodically come into play with stationary blades. The rotation of the impeller grinds the waste into a pulp and circulates the water in the tank. Waste particles that are sufficiently small are discharged from the tank and pass through a conduit to the liquid extraction assembly.
The extraction assembly typically includes a vertical or near vertical feed screw surrounded by a cylindrical screen. The flighting of the screw has brushing extending radially out to the diameter of the screen. The brushing keeps the holes in the screen clear, and helps move solids in the annular region between the outer diameter of the flighting and the screen upward towards the top of the extractor. The screw rotates at a speed between 85 and 90 revolutions per minute, to advance the solid particles within the pulp vertically towards the top of the extractor. The water within the pulp drains out through the screen due to gravity, and is returned for re-use in the tank. Some systems have included inverted conical restrictor elements at the top (discharge) end, to compress the solid material before discharge for additional liquid removal. The partially dried material at the top of the feed screw is then removed for disposal.
The waste reduction systems developed in the prior art occupy a large footprint and the extractors are typically very tall, often 2 meters in height. The prior art waste handling systems also have been expensive to manufacture (and purchase). Installation often requires technicians to install lengthy conduits between the pulper unit and the extractor unit. To improve the footprint, some "close coupled" systems have been developed. These systems have a relatively short distance (e.g., about 30 centimeters) between the pulper and the extractor.
After installation, the prior art systems typically require frequent maintenance by trained personnel after installation. Impeller blades have been prone to damage when non-pulpable objects (e.g., metal flatware) become lodged in the blades. Blade replacement is a delicate operation requiring a skilled technician. The extractor unit also requires relatively frequent maintenance, to ensure that particles do not clog the openings in the screen or become hardened on the flighting of the screw. The brushing must be replaced fairly often, which is difficult and time consuming. Removing the screw and screen is a complex operation also requiring a technician.
The large space requirement and operating costs have typically limited the use of these waste reduction systems to large institutions, such as hospitals, large hotels and cruise ships. The systems have generally not been practical for small institutions (e.g., restaurants) that generate the same types of waste as the large institutions, albeit in smaller quantities.
Another disadvantage of prior art waste reduction systems is the need for an operator to manually feed articles of waste individually into the pulper. Prior art systems have typically employed a chute or water fed trough into which the articles are manually placed for disposal. Fast food restaurants produce large quantities of trash and garbage in bags collected from receptacles commonly referred to as "Thank You" boxes. Prior art waste pulping systems do not process full bags well; the bags must be opened or torn, and the waste manually fed into the pulper in small batches. This process is labor intensive.